1. Field of the Invention
The invention relates to portable display devices and programs, and more particularly to portable display devices and programs for maintaining a display image or information in the portable display devices even when power from a power source is turned off.
2. Description of Related Art
A known portable display device, e.g., electronic paper viewer, e.g., a device described in Japanese Laid-Open Patent Publication No. 2007-187927, includes a non-volatile display device configured to maintain display information, e.g., an image, even when power supply from a power source is turned off. The portable display device is configured to maintain information, when power is turned off. Therefore, a user may view the information even in a state of power-off. Another known portable display device is configured, for security reasons, to erase information displayed in a non-volatile display device immediately before power is turned off and make different display, e.g., display another information such as textual information, e.g., “Power off,” in the non-volatile display device.
In the above-described display devices, a user is not able to select which information is displayed in a state of power-off, information displayed immediately before power is turned off, or another information, e.g., different display. Thus, information that a user desires may not be displayed in the non-volatile display device in a state of power-off, which may be inconvenient for users. Further, information that the user would not like to show other users may be unintentionally displayed in the non-volatile display device.